The purpose of the proposed project is to determine whether individuals undergoing total hip or knee replacement procedures with medical devices containing chromium experience an elevation in the levels of DNA-protein crosslinks (DPC), a highly sensitive marker of early biological damige from exposure to chromium. The specific aims are: * To assess whether the levels of DPC in peripheral lymphocytes of joint replacement patients increase after the surgical procedure. * To assess whether changes in circulating chromium concentration correlates with changes in levels of DPC. * To study the time-lag between surgery and the increase in levels of DPC. Since hip replacement patients have already been observed to be at increased risk for development of connective tissue tumors, as well as cancers of the kidney and prostate, the DPC assay has the potential to become a monitoring tool to detect any long-term health consequences from metal prosthetic devices containing chromium. Fifty study participants will be recruited among patients undergoing hip or knee replacement procedures. Blood will he collected prior to surgery to establish a baseline measurement. Each participant will be followed up at four periodic intervals for 12 months. In addition to the DPC assay, circulating chromium concentration will be measured.